The invention relates to a receiver scheme, and more particularly to a radio frequency receiver front-end.
Generally speaking, a conventional receiver consists of a low-noise amplifier (LNA) for improving SNR, a mixer for frequency conversion, and a low-pass filter to filter out unwanted signals for channel selection. The linearity of the conventional receiver is usually limited by the LNA and mixer. To achieve high linearity, a conventional scheme may configure the output impedance of LNA to be a low impedance and pair with a passive mixer which has good linearity due to it passive nature. To achieve the low output impedance, the conventional scheme may employ a transimpedance amplifier (TIA) wherein the TIA has a low input impedance at baseband and this low input impedance can be frequency-translated to LNA output at RF frequency through the passive mixer. In addition, to suppress impairment introduced by a passive mixer, the mixer size has to be larger to minimize adding extra mixer switch impedance to the required low impedance path. Unfortunately, the larger mixer size requires larger LO drivers, and hence causes larger power consumption for the LO driver. The LO driver is the major power consumption contributor. In addition, for TIA to generate low impedance at its input, a large current consumption is required to maintain low noise and low impedance across the bandwidth. The TIA is another major power consumption contributor. It is a key issue to reduce larger power consumption from the LO driver and TIA for a ultra-lower power receiver design.